I. Field of the Invention
This invention relates generally to electrical transient suppression apparatus which utilizes varistors connected from each electrical phase to neutral as well as a varistor connected from electrical neutral to ground to protect the electrical system and connected equipment from high voltage transients and surges. A protective case, made of high impact plastic having good insulation properties, protects this electrical circuit. The protective case is devised to assist in assembly, to provide a support for potting the electrical circuit, to seal readily to standard electrical circuit boxes and to protect the wires.
II. Description of the Prior Art
There are a number of transient suppression circuits which address the problem of apparatus and equipment protection from high voltage transients and surges.
In U.S. Pat. No. 3,546,572, Specht et al varistors in parallel with capacitors are connected only from each phase leg to neutral as clamping devices to suppress high voltage surges. In U.S. Pat. No. to De Cecco et al, 3,947,726, varistors in series and in parallel with other circuit elements are used as a surge-energy dissipating process. These patents are representative of the prior art.
No prior art known to me provides the combination of the attributes of the present invention, namely, varistor protection, not only between each electrical phase and neutral, but also between the neutral and ground circuits with the circuits in a protective insulated container capable of meeting the explosion-proof, waterproof and acid-proof requirements of the National Electrical Code and capable of being connected and sealed readily to existing standard electrical circuit boxes with an enclosure devised to permit potting, providing wire protection and automatic strain-relief during assembly.